Blood dialysis for patients suffering from renal insufficiency has been carried out for about 10 years, and abnormalities, such as flexor canal syndrome, have been revealed. In recent years, it has turned out that such abnormalities are caused by .beta..sub.2 -microglobulin. .beta..sub.2 -microglobulin is relatively hard to remove by dialysis and various symptoms are manifested through accumulation of this substance within the body.
Blood filtration and dialytic filtration have conventionally been employed for the purpose of removing such a medium-molecular weight substance. These techniques, however, attain low rates of removal and require a large quantity of a replenisher for achieving effective removal. Although the rate of removal may be increased by making the pores of the membrane employed larger, a small increase in pore size results in loss of albumin, a useful protein. Under the present situation, therefore, control of pore size cannot achieve effective and selective removal of medium-molecular weight substances.
JP-A-62-240068 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application") discloses an adsorbent for .beta..sub.2 -microglobulin, but the adsorption performance of this adsorbent is insufficient. Further, JP-A-62-204761 discloses various adsorbents for in vitro circulation which comprise a carrier having supported thereon a ligand. However, this reference does not refer to an adsorbent for .beta..sub.2 -microglobulin.